Energy is transported by ocean waves. In the pursuit of energy sources having a low carbon footprint, there has been much work in the conversion of the energy of ocean waves into useful forms of energy, such as electricity. One field of such work is focused on so-called point absorbers. Point absorbers are effectively individual buoys floating on the surface of the ocean which undergo displacements due to incident ocean waves. This displacement can be used to convert wave energy into useful forms of energy. An example of such a point absorber is given in WO 99/22137.
Further, it is known in the field of wave energy conversion to use pre-tensioned buoys. Pre-tensioning of a buoy (e.g. by in some way forcing it to submerge to a depth greater than its natural floating depth) has the effect of providing a negative mass to the oscillating system, and hence effectively reducing the inertia of the buoy, and increasing its response to incident waves.